National Radio Astronomy Observatory

NRAO Makes Wealth of Fresh Astronomical Data

Accessible by Information Superhighway

An original and comprehensive data set potentially full
of scientific surprises now is available to astronomers, students
and the public through the information superhighway. Radio images
of the sky produced by the Very Large Array radio telescope -- one
of the premier astronomical instruments in the world -- as part of
a massive survey now are stored in an electronic repository avail-
able over the Internet computer communications network.

"Each of these sensitive new sky maps shows about a thou-
sand radio-emitting objects, most of which have never been seen
before," said Dr. J. J. Condon, leader of the National Radio As-
tronomy Observatory (NRAO) survey team. "We are releasing them as
soon as they are completed because they contain more data than we
could possibly analyze by ourselves."

"By using electronic distribution, we can open this tre-
mendous resource of information for computer analysis by all as-
tronomers immediately, without waiting for traditional
publication," Condon added. The radio images are copyright NRAO/
AUI. Permission is granted for use of the material without charge
for scholarly, educational and private non-commercial purposes.

"It is entirely conceivable -- even probable -- that
valuable discoveries will be made by students or amateur astrono-
mers who devote the time to study these maps carefully," said team
member Dr. W. D. Cotton. "Making this new information available
electronically means that more people can participate in adding to
its scientific value."

The maps are a product of the NRAO VLA Sky Survey (NVSS),
which began its observational phase in September of 1993 and will
cover 82 percent of the sky when completed by the end of 1996. The
NVSS is expected to produce a catalog of more than two million ra-
dio-emitting objects in the sky, and it is the first sky survey
sensitive to linearly polarized emission from radio sources beyond
our own Milky Way galaxy. "The NVSS is being made as a service to
the entire astronomical community," Condon said. The survey will
require about 2,500 hours of VLA observing time to complete.

The data from the NVSS will become available in several
forms, including complete processed maps, lists of the radio-emit-
ting objects found, and data from which astronomers may produce
maps tailored to their own interests. The data products are being
placed in the public electronic repository as soon as NRAO scien-
tists have verified their accuracy. Those interested should contact
Condon at Internet address jcondon@nrao.edu for more information
about accessing the data.

The Very Large Array, in west-central New Mexico, is a
radio telescope consisting of 27 dish antennas, each 82 feet in
diameter, arranged in the shape of a Y. The arms of the Y are 13
miles long, and the 230-ton antennas are routinely moved into dif-
ferent positions along the arms to provide a "zoom lens" capability
for the telescope. Dedicated in 1980, the VLA is used annually by
more than 600 astronomers from around the world. One of the most
versatile instruments available to astronomers, it can observe ob-
jects ranging from planets, comets and asteroids in our own solar
system out to distant radio galaxies and quasars near the edge of
the observable universe.

In addition to the NVSS, the VLA also is making another,
more detailed, survey of a smaller region of the sky. This survey,
called FIRST (Faint Images of the Radio Sky at Twenty centimeters),
will yield very accurate positions of radio-emitting objects in the
same area of the sky to be surveyed in visible light by the Sloan
Digital Sky Survey. The FIRST survey is headed by Dr. Robert H.
Becker of the University of California at Davis and Lawrence Liv-
ermore National Laboratory.